The invention generally relates to an arrangement to fasten ceramic to metal components within a turbine engine.
Exhaust within and leaving turbine engines is at extremely high temperatures. The measured temperatures from the turbine engine and exhaust are known as an engine's heat signature. Turbine engines for use in military aircraft have performance requirements relating to reduced measured heat signatures. As the components of the turbine engine absorb heat, the heat signature of the turbine engine is increased.
Ceramic matrix composite (CMC) materials provide surfaces with a greater ability to absorb heat than the metal materials typically used in turbine engines. To reduce the absorption of heat by engine components resulting in a lower heat signature, a turbine engine exhaust nozzle is lined with CMC components. CMC components are attached to metal structural components of the turbine engine to line the interior of the engine.
CMC components are lighter than metal components, but raise the challenge of being difficult to attach to the metal structural components of the turbine engine. In part, this results from a reduced thermal growth rate of the CMC components when compared to the metal components. The CMC materials also have low ductility compared to the metal components and unless preload is applied, the CMC component will vibrate against the metal components, causing damage. Additionally, many applications require that the CMC components be attached using a CMC fastener, rather than a metal fastener.
Thus, when attaching the CMC materials to the metal structures in a turbine engine, it is desired for the fasteners to allow for the increased thermal growth of the metal structural components compared to the CMC components. Additionally, the fastener must apply a preload to the CMC component to reduce vibrations.
A fastener to secure CMC components to a metal structure in a turbine engine while applying preload and allowing for differing thermal growth rates is desirable.